a) Field of the Invention
The present invention relates to a sheet discharger for an image recording apparatus such as an Xerographic copying machine and a printer, and in particular, to a sheet discharger capable of discharging printed sheets on which images have been recorded while sorting these sheets in a page order. The present invention is particularly applicable to a sheet discharger employing a vertically arranged sheet discharge tray of a type that is arranged obliquely backward with respect to an upper, vertical direction, but may also be used with a commonly known sheet tray that is arranged obliquely upward with respect to a sheet discharging direction.
b) Description of Related Art
In case a plurality of pages are printed out from an image recording apparatus such as a low cost printer, it would be appreciated in view of user's comfort that the printed sheets of the plural pages are discharged while being sorted in a page order.
In contrast, a commonly known sheet discharger discharges the printed sheets with the printed surfaces thereof being oriented at the upper side, so that a succeeding printed sheet is discharged onto the printed surface of the preceding printed sheet, and thus the printed sheets are set in the reversed order. That is to say, the sheet discharger of this type suffers from a problem in that a user is required to perform an additional workload sorting the printed sheets in the page order after completion of printing.
Various attempts have been proposed in the art to solve the above-mentioned problem.
The first one is directed to a technique with the use of a large-capacity memory, wherein all of data read from the original image or print data thereof are first stored in the large-capacity memory, and then the printing operation is carried out from the final page. According to this technique, the pages of the sheets are sorted when the printing operation is completed, and further since the printed surfaces of these pages are directed upward, the printing conditions of these printed sheets can be immediately confirmed. Thus, very good operability can be achieved. However, since this technique requires a large-capacity memory, there arises another problem the cost would be considerably increased.
The second technique is to discharge a sheet after the sheet is inverted. Accordance to this technique, the printing operation is sequentially carried out from the first page of the sheets, and each sheet is discharged to the discharge tray to face downwardly. That is to say, the preceding, first page is discharged with its print surface oriented downwardly, and the succeeding, second page is discharged onto the reverse side of the first page with its printed surface oriented downwardly. Therefore, the copy or print sheets can be sorted in the desired page order at the same time when the copy sheets are discharged to the discharge tray. However, this conventional method necessarily requires such extra operations that the printed sheets are once turned over. Also, in accordance with this conventional method, the printed surface cannot be completely observed unless the sheets must be turned over. In general, users intend to confirm, due to their satisfaction, that no fault is made in the printed condition of the first page of the printed sheets. When the printed surface of the sheet is discharged downwardly, as described above, the users would have fear as to whether or not the desirable printed condition could be achieved.
There are other proposals, namely as disclosed in Japanese U.M. publication No. 61-36523, Japanese Laid-open U.M. application No. 63-26661, and Japanese Laid-open Patent Application No. 63-185770.
In these conventional sheet discharging methods, the second page and subsequent pages of the sheets are inserted into the lower side of the previously discharged sheet. Since the subsequent sheets are inserted while the weights of the sheets previously discharged are influenced to these subsequent sheets, it is very difficult in these conventional sheet discharging methods to discharge the second page and subsequent pages of the sheets into the tray.
Any of the above-described prior art is directed to such a method for discharging the sheets into the discharge tray which has not so large inclinations with respect to the horizontal line (will be referred to a "horizontal (transverse) type sheet discharge tray") in such a manner that these sheets are overlapped with each other.
In contrast to the image recording apparatus with employment of the horizontal type sheet discharge tray, there is another image recording apparatus with using a vertical (longitudinal) type sheet discharge tray which is inclined backwardly along the Upper direction. When such a vertical type discharge tray is employed, the vertical (longitudinal) type paper supply tray is normally employed. Since such a vertical type tray is used, it is possible to reduce an installation area required to install the image recording apparatus.
The above-explained conventional vertical type sheet discharge tray is arranged above the discharge roller apparatus constructed of the front side discharge roller and the rear side discharge roller. This vertical type sheet discharge tray has the rear surface supporting member for supporting the rear surface of the discharged sheet and the bottom member for supporting the lower end (edge) of the discharged sheet.
The conventional vertical type sheet discharge tray has such a structure that the discharged sheets are rest against the rear surface supporting member whose upper portion is backwardly inclined. Then, after the sheet of the first page has been discharged while the printed surface thereof is directed to the front side, the sheet of the subsequent, second page is stored in such a way that the printed surface of the second page is overlapped with the front printed surface of the first page while being directed to the front side.
As described above, this conventional vertical type sheet discharge tray has such a structure that the subsequent printed sheets are successively overlapped on the front surface of the previously discharged printed sheet. Therefore, both the rear-surface supporting member and the bottom member of the vertical type sheet discharge tray are arranged so that these members are positioned at the rear side of the discharge roller of the discharge roller apparatus installed below.
In this conventional vertical type sheet discharge tray, the second page of the sheet is overlapped on the printed surfaced of the first page, so that the sequence of the overlapped printed sheets is reversed. As a consequence, after the printing operation is completed, the pages of the sheets must be sorted, which may cause such a problem that unnecessary workloads would be given to the users.
As the method for solving this problem of the vertical type sheet discharge tray, it is conceivable that the bottom member of the vertical type sheet discharge tray is arranged at the front side of the discharge roller apparatus, and the front surface supporting member for supporting the front surface of the discharged sheet is provided at the front end of the bottom member. In this case, the front surface supporting member is arranged in such a way that the upper portion thereof is inclined along the forward direction. With employment of such a construction, the first page of the sheet is discharged with the printed surface thereof being directed downwardly over the front surface supporting member, and then the second page of the sheet is discharged in such a manner that the printed surface of this second page is downwardly directed to the rear surface of the first page of the sheet.
Thus, the printed sheets can be stored into the vertical type sheet discharge tray under such a condition that the sequence of the overlapped printed sheets are sorted in the normal order from the first page.
However, in this conventional solution method, no printed surface of the discharged sheets can be observed.
As a consequence, since the users cannot confirm as to whether or not the printing condition of the first page contains faulty, they may fear that the printing operation is carried out under desirable conditions.